Charge forming device



Sept. 2, ML J. w. HOGG CHARGE FORMING DEVICE Original Filed Marqh 26. 1934 2 Sheets-Sheet '1 \k MN a .3 Q a i A. m

I "..........nununfll Sept. 2, 1941. v.1. w. HOGG CHARGE FORMING DEVICE 2 Sheets-Sheet 2 r I i m a IF? Original Filed March 26, 1934 IIIII I n-II IIIIII lrllll/lmnunnnnnn van-nun";

Reissued Sept. 2, 1941 CHARGE FORMING DEVICE John Webb Hogs, Llanerch, Pa., assignor to Bendix Aviation Corporation, South Bend, Ind, a corporation of Delaware Original No. 2,004,869, dated June 11, 1935, Se-

rial No. 717,476, March 26,1934.

Application for reissue June 25, 1940, Serial No. 342,390

, 13 Claims.

This invention relates to charge forming devices; and it comprises apparatus for supplying and mixing two fluids in fixed relative proportion,

flow, means adapted to respond to said fuel flowdifferential pressure and means adapted to' respond to said air flow differential pressure, each of said pressure responsive means being adapted to operate the valves, means for combining the two flows, and throttling means for varying the total amount of combined flow; all as more fully hereinafter set forth and as claimed.

In many chemical processes and operations it is necessary tomix two different fluid flows, such as gases or liquids, in fixed relative proportion,

under varying rates of combined flow. In many cases the pressure on the two component fluids fluctuates, as by variations in hydrostatic head, in pump pressure, etc. It has been a desideratum to provide a simple means for automatically proportioning and mingling two component fluids in constant relative proportion, independently of fluctuations in pressure in either component fluid or of fluctuations in the total amount of combined flow.

Thepresent invention provides simple means adapted to automatically mix two fluids in ,con-

stant proportion. While it is of general application, it will be described in a particular application: embodied in a carburetor for internal combustion engines.

In the internal combustion engine art it is customary to supply to the cylinders air and a flow of fuel, which may be gas, gasoline or oil. When liquid fuels are used, it is usual to provide for sprayingv or vaporizing the fuel, before it reaches the cylinders. Various types of carburetors and mixing valves have found use for performing these functions. In general they comprise, in the case of gasoline motors, an air conduit leading to the intake of the cylinders, and means for introducing liquid gasoline into air flowing through the conduit. The conduit is usually provided at some point with a venturi or other means for producing an area of reduced pressure, that is high suction; and the gasoline is introduced at this point, as by a jet or jets. In the usual carburetor some sort of throttle device for the air-gasoline mixture is provided: a butterfly valve or the like.

In many cases it is desirable to provide a substantially constant proportion of gasoline and air at different throttle openings and at different rates of air flow; that is at different engine speeds and loads. The simplest form of carburetor, comprising merely a gasoline jet opening into the air intake conduit, while it may be designed so as to deliver the correct mixture for one given engine speed, does not then provide uniform proportioning at different loads and speeds. engine speeds, the flow of air into the engine increases, but the proportional amount of gasoline taken up by the air increases faster than the rate of air flow. Hence, with this sort of elementary carburetor, if it is adjusted correctly for medium speeds then at high speeds it will deliver a mixture too rich in gasoline. This defeet is inherent in the'simple type of carburetor described.

Most modern carburetors for variable speed engines represent additions to, or modifications of,'this elementary form of carburetor, with the object of adapting it'to deliver a more or less constant mixture at all speeds. In some types, an auxiliary air valve is provided, adapted to open to a greater or less degree at higher engine speeds to dilute the over-rich mixture furnished by the jet. Some types make use of metering .pins, valves in the fuel line linked to the throttle,

or multiple gasoline Jet devices in which different numbers of jets-are thrown into action at different engine speeds; all with the idea of securing correct proportioning under different speeds and loads.

None of these devices is entirely satisfactory in operation. In carburetors of the simple air valve type, for example, having a spring-restrained flapper-valve adapted to be opened under intake suction. the'mixture is by no means constant at different speeds. There is apt to be an abrupt change in proportioning when the spring comes into action; and moreover the nature of the restraining force exerted on the air valve by a cylindrical coil spring is such that the air valve opening is not strictly correct except at one given speed. Attempts have been made to control the air valveby means of double springs, tapered springs, etc. but these are still not satisfactory in insuring correct proportioning and moreover are likely to get out of adjustment.

According to the present invention I provide At increased a carbureting device adapted in its basic form to automatically supply to an engine a constant ra-' tio of air to gasoline under different loads, different speeds, and different pressures in the. fuel line and air intake. I do this by providing linked valves in the fuel inlet line and in the air intake conduit, pressure responsive means in the'fuel line and the intake conduit, and means whereby the pressure responsive means control the valves according to pressures'in the fuel line and the intake conduit.

The present invention also contemplates a carburetor for internal combustion engines including an air conduit delivering to a mixing chamber in communication with the engine intake, a fuel conduit delivering fuel at a jet in the mixing chamber, means for establishing differential pressure in each conduit, a variable opening valve in the fuel conduit, means responsive to the differential pressure in the fuel conduit and operatively connected to the valve to reduce the valve opening on increase in differential pressure in] the fuel conduit, and means responsive a different proportioning in some parts of the operating range, as for example to supply a slightly leaner mixture at high engine speeds and thus secure economy. The new device is simple but presents several advantages over ordinary carburetors. bowl and is able to function properly in any position. Moreover it is well adapted for use in conjunction with a supercharger. Hence it is Well suited for aircraft engine carburetion.

In the accompanying drawings I have shown several forms of a specific embodiment of my invention.

' Fig. l is a view in vertical section of a carburetor for liquid fuels;

Fig. 2 is a view in vertical section of a modified form of carburetor Fig. 3 is a view in vertical section of a modified form of carburetor employing sliding seats;

Fig. 4 is a view in vertical section of a modified form of mixing device;

The device employs no float with the high pressure (inlet) side of the orifice,

- tional to the square of the velocity of the fluid Fig. 5 is a view partly in vertical section and partly in elevation of a modified form of carburetor employing Venturi differential pressure establishing means; and

Fig. 6 is a similar view of a modification em-- ploying Pitot tube differential pressure estab- .lishing means.

In the drawings, in which like reference characters indicate like parts throughout, Fig. 1 shows a carburetor device comprising a mixing chamber In adapted to be attached by means of a flange I I to the intake manifold (not shown) of an internal combustion engine. A throttle valve l2 of the ordinary butterfly type is mounted in the chamber as shown. Other forms of throttling devices may be employed. The flow proportioning means comprises a valve l3 for fuel and a valve l4 for air. The two valves are mounted on a single shaft l5 as shown and cooperate with conical seat members 16 and I1. The mixing chamber is merged, as shown, with a cylinder I8 communicating with an intake contition or plate 23 having a restricted orifice 24 is end of shaft I5 is attached as at M to a piston 22 adapted to slide freely in cylinder l8 while maintaining a relatively leak-proof sea]. A parmounted in the intake conduit as shown. The restricted orifice produces a differential pressure across the partition, when air is flowing through the conduit. -A conduit 25 connects the space 26 in the cylinder behind the piston with the intake conduit before the orifice, as shown. The conduit puts one side of the piston in communication while the other side of the piston is in communication with the low pressure side of the orifice. The differential pressure across the orifice. and hence across the piston, will be proporpassing through the orifice.

A second cylinder 30 is mounted in the mixing chamber as shown, in opposed relation to cylinder I3. A piston 3| attached as at 32 to the other end of shaft I5 is adapted to slide freely, but without substantial leakage, in cylinder 30. Fuel enters the cylinder on one side of the piston through a fuel inlet conduit 33 and inlet 34, and on the other side of the piston through an inlet 35. A partition 36 having a conical restricted orifice 31 is positioned in the fuel inlet line between inlets 34 and 35, as shown. With this arrangement, when fuel enters inlet 33 under pressure and flows across orifice 31 a differential pressure is set up across piston 3|. The differential pressure is proportional to the square of the velocity of the entering fiow of fuel. A tapered pin 38 cooperating with orifice 31 is provided for regulating the differential pressure across the orifice. The tapered pin is mounted on a threaded shaft 39 rotatably mounted in the inlet line as. shown and provided with a handle 40 by which the tapered pin can be secured to different positions in the orifice. One end of cylinder 30 projects into the mixing chamber as shown. The cylinder is capped as at and a small orifice 45 is provided fitting shaft 15 closely while allowing free motion thereof. Seat I6 is mounted in the cylinder by means of a partition 41. An elongated nipple 48 l is mounted on the end of the cylinder, projecting into the mixing chamber as shown, and in communication with the cylinder beyond partition 41. The nipple is provided with a narrow bore 43.

In operation, air flows into the mixing chamber through conduit l9 and valve and seat ll, l1; either under engine suction or under pressure as by a blower or super-charger. Fuel is supplied to inlet 33 under pressure, as from a pump or from an elevated source of supply, and enters the mixing chamber through orifice 31, inlet 34, valve and seat I3 and I6, and bore .43. In the air side of the carburetor, a differential pressure is set up across orifice 24 and the pressure on the right hand side of the orifice being greater, pressure in space 26, in communication with intake I3 through conduit 25, tends to force the piston 22 to the left, partially closing the air intake past valve and seat l4 and H. At the same time, a differential pressure is set up across fuel conduits 34 and 35 by means of orifice 31, and pressure to left of piston 3| tends to move the piston to the right, partially closing the fuel flow through valve and seat [3 and i6. According to the invention the size of cylinders l8 and 30 of orifices 24 and 31, and of the fuel and air valves is so proportioned that when fuel and air are supplied under normal relative flows the tendency of the air piston, under differential pressure in the air flow, to

move shaft I'in one direction, is exactly counter pistons are in general not equal. In the balanced position, the pressures on the pistons are only equal when the two pistons are made the same size. But the opposing forces exerted by the two pistons are equal and balanced. The tapered pin in the fuel line permits the differential fuel pressure across piston 3| to be adjusted; and hence the relative proportion of fuel and air.

If the suctionin air intake conduit I9 is inopening the, throttle, the pressure differential across orifice 24 will increase, increasing the pressure in space 20 and moving the piston 22 and hence shaft I5'slightly to the left. This cuts creased, as by an increasein engine speed on down the air flow slightly and opens fuel valve I3 slightly, thereby admitting more fuel into the increased air flow.

' Similarly, if the pressure in the fuel line increases, the fuel valve I3 will partly close and the air valve will open, admitting more air and thus keeping the proportions constant. The

throttle valve I2 allows the total combined flow to be regulated.

This embodiment of the invention is well adapted for use inalrcraftengines, which are ordinarily equipped with a fuel pump and a supercharger. The device dispenses with neat bowls, vacuum tanks, etc., and is thus capable of functioning satisfactorily in any position. The fuel injection nipple 4B is short and finebored; thus neither gravity nor suction in the air intake near the nozzle hasany appreciable effect on the rate of introduction of fuel.

Fig. 2 represents a modified form of carbureting device in. which thepistons are replaced by diaphragms. This construction presents some advantages in that diaphragms are free from friction. As shown, the air side of the carburetor is similar to that in Fig. 1, except that piston'22 is replaced by a corrugated, flexible metaldia phragm 55 fixed in the cylinder as at 5B and centrally attached to shaft I5 as at 2|. 0n the fuel side, cylinder is replaced by an injection nozzle 51 mountedin the mixing chamber as shown and provided with a tapered orifice 58 cooperating with valve I3 as shown. The nozzle is in communication with a diaphragm chain ber 59 containing a diaphragm 60 mounted therein as at BI and centrally attached to shaft I5 at 32. Inlet is in communicationwith one side of the diaphragm and inlet 34 with the other side. The rest of the device of Fig. 2 is similar to Fig. l. The operation is the same and requires no further explanation.

Fig. 3 shows a modified form of carbureting device having balanced valves, in which the throttling'is effected by shifting the valve, seats and which also has provision for changing the relative proportions of fuel and air in certain parts of the operating range. As shown, the device comprises a cylindrical mixing chamber I0 with flange II. The air side of the device comprises a cylinder 10 mounted on' the mixing chamber as shown. A separator disk H having a circular orifice I2 is mounted in the mixing chamber as shown, and a similar separator disk I I3 having a circular orifice II is mounted in the chamber below thefirst disk and adjacent the lower rim of cylinder I0 as shown. A vertical cylinder I5 is positioned concentrically within the mixing chamber, as shown, joining the edge of orifice I4 as at I6 and joining the upper disk 'II as at H. The air valve is a balanced valve comprising two discoid valve members I8 and 19 mounted'on a shaft attached as at 8| to a sliding piston 82 adapted to slide freely in cylinder I0. The piston is orificed as at 83: in this embodiment the differential pressure is established by means of orifices in the piston itself. The valve members I8 and I9 cooperate with two comically orificed seat members 00 and 9|. These seat members are coupled together by means of a rod 92 as shown, and are adapted to slide in-two cylindrical slides or ways 93 and 94. It is seen that the valves are in communication with an annular space 95 bounded by the outer wall of cylinder I5, the inner wall of chamber I0, and separators H and I3; and in communication with an inner cylindrical space 96 in the cylinder I5. Air passes into the mixing chamber through valve and seat 18, and through valve and seat I9, 9I.

In. the'fuel side of the carburetor, the arrangement is similar. I A cylinder I00 is mounted in the mixing chamber as, shown. A piston IOI orificed as at I02 slides in the cylinder; The piston is attached to a shaft I03 as at I04. Two discoid valve members I05 and I06 are mounted on the shaft as shown and cooperative with two sliding seats I01 and I08, which are coupled together by a rod I09. The seats are adapted to slide in cylindrical ways III! and III which aremounted in a cylinder II5 similarly to the arrangement of the air valves. Fuel is admitted to cylinder I00 through inlet 33. Valve shaft I03 and 80 are coupled or attached to each other by a bar IIB so that movement of either shaft is directly com municated to the other shaft. The sliding seats, coupled by rods 92 and I09, are adapted to be moved from outside by means of a rotating lever I2I pivoted in the walls of, cylinder I5 and the mixing chamber by a rod I22 and pivotally attached to rods 92 andI09 as at'l23 and I24. The outer end of rod I22 carries an arm I25 adapted to be operated by throttle rod I25 as shown. Movement of the arm is thus communicated to rods 92 and I09 and allows the seats to be shifted from outside, with respect to the discoid valve nearer the valve members, throttling the flows of fuel and air.

As stated, it is often desirable'to provide for richer or leaner mixtures than are theoretically correct, in certainparts of the operating range.

In Fig. 3 I have shown how. the deviqe may be,

modified to provide this. 'As shown, a tapered or graduated pin I30 is mounted in cylinder I00 by means of the threaded rod I3I carrying a handle I32 and cooperating with orifice I02 in piston Throttling is performed by moving- II". The tapered pin, which is stationary with respect to the orifice I02 is adapted to provide different effective orifice openings in different operating positions of the valve and piston linkage. If the fuel flow is, for example, under substantially constant pressure, as is the case when an ordinary vacuum tank fuel supply is used, and the air flow varies according to the throttle opening and engine speed, their different rates of air flow will produce different effective orifice openings in the fuel piston, and hence the opening of the fuel valve will change in such a way that different fuelair proportions will be provided for different air fiows. The proportions of fuel and air may be varied in any part of the range by providing the tapered pin with a suitable con-tour. In Fig. 3 the contour of the pin is such that movement of the valve linkage to the left under increased air flow'cuts down the effective orifice at I02. The fuel pressure being assumed constant, the result is that under increased air supply the proportional fuel supply is slightly less than when a simple orificed piston, without tapered pin, is used. Thus a slightly leaner mixture will be provided under increased air flow; at higher engine speeds. In some cases it is desirable to have the tapered pin almost cylindrical, thereby producing but slight change in proportioning in different parts of the operating range. In some cases it is found convenient to have the taper of the pin reversed;

that is, the large base of the pin is on the right of piston IIII and the smallest section is to the left.

'I have shown cylinder III in communication with an air cleaner indicated diagrammatically at I33. The use of an air cleaner is desirable but is not essential.

The double valve arrangement shown for both fuel and air fiows is to provide balanced valves. In the air valve for example flow in one direction through valve and seat I8 and 90 is balanced by flow in the opposite direction through valve I9 and seat 9| Thus there is no disturbing effect due to rush of air against the discoid valve members. The fuel valve arrangement is similar.

In Fig. 4 I have shown a simplified form of charge forming of mixing device adapted for use with gas engines, or for general fluid proportioning. As shown, the device comprises a mixing chamber III in communication with an inlet cylinder I40 for one fluid and an inlet cylinder I for another fiuid. -Two conical valve seat members It and II are mounted in the device by partitions I42 and 2|) as shown. The valve assembly comprises two discoid valve members I43 and I44 mounted on the shaft I5 which is attached as at 32 to an orificed piston I46 sliding in cylinder Ill and attached at the other end as at 2I to an orlflced piston I41 sliding in cylinder I40. The

operation of the device is similar to that of Fig. 1.

Figs. 5 and 6 show embodiments of the invention similar to that of Fig. 2 but making use of Venturi and Pitot tubes respectively for the differential pressure establishing means. .Thus in Fig. 5 the fuel conduit restriction 3G is replaced by a Venturi passage I5II, to which the high and low pressure connections 34 and 35 are made as shown. The fuel conduit 33 is joined to passage 51 at I5I, and a bored partition I52 separates the low pressure space at the right of diaphragm GII from the passage 51. The air differential pressure establishing means comprises a venturi I53 disposed in an exactly similar manner. Conduits I54 and I55 connect the venturi I53 and the intake conduit I 9 respectively with the chambers I56 and I5'I to the right and left of diaphragm 55. A partition I58 separates the chamber I51 from the air passage I8 and is provided with a bearing I59 which closely receives the shaft I5 to prevent any substantial leakage therepast.

In Fig. 6 the high and low pressure fuel connections I34 and I35 terminate in a Pitot jet I62 and a static-pressure jet I63 as shown, and a similar arrangement and similar jets I65 and I66 are employed in the air conduit I 9 as shown, connected through conduits I61 and I68 to the chambers I56 and I5! on opposite sides of the diaphragm 55.. A partition I58 separates the low pressure side of the diaphragm from the air passage I8. The functioning of the apparatus of Figs. 5 and 6 is similar to that of Fig. 2 and requires no further description.

For the sake of clarity the invention has been shown diagrammatically. In devices constructed according to the invention the various parts are proportioned to suit the requirements of the installation for which the device is intended. The usual attachments for carburetors, such as choker valves, warmers etc., may be employed, these being omitted from the drawings for the sake of simplicity. Also the pressure responsive means in each device may be diaphragms, multi-convolution bellows or pistons, and the means for establishing differential pressures for operating the pressure means may be of the orificed partition, Venturi or Pitot tube type, as isconvenient. The tapered pin valve in the fuel line can be mounted in such a way as to allow it to be temporarily retracted from the valve seat by a hand lever or other control means, to provide a temporary increase of the fuel fiow as during starting up.

What I claim is: I

1. Apparatus for mixing two fluids under pressure in constant relative proportion, comprising a conduit for each fluid, the conduits being in communication, a valve in each conduit, means coupling the valves together, means separate from said valves for establishing a substantial differential pressure in each fiuid and means responsive to 'said' differential pressure of each fluid and operatively connected to the valve for actuating the same.

2. Apparatus for mixing two fluids under pressure in constant relative proportion, comprising a conduit for each fluid, the conduits being in communication, a variable opening valve in each conduit, coupling means for the valves such that motion of one valve towards closed or open position respectively imparts motion to the other valve towards open or closed position respectively, means responsive to variations in pressure of the fluid in each conduit resulting from variations in the fiow of fluid therethrough, said pressure responsive means beirg operatively connected to the valve coupling means whereby increase of flow in either conduit is adapted to partially close the valve in that conduit and to partially open the valve in the other conduit.

3. In a carburetor for an. internal combustion engine a conduit for fuel and a conduit for air, a mixing chamber in communication with the conduits, a variable opening valve for each conduit adapted to control flows therein, coupling means for the valves, means separate from the valves for establishing a substantial differential pressure in each flow, means responsive to said differential pressure of fuel and of air in operative connection with the valves and means for varying the total combined flow from the mixing chamber.

4. Apparatus for delivering a flowing mixture of fuel and air to an engine in definite relative proportion and in variable total flow, comprising a conduit for fuel and aconduit for air, a mixing chamber in communication with said conduits, a variable opening valve in each conduit, coupling means for the valves such that motion of one valve towards closed or open position respectively imparts motion to the other valve towards open or closed position respectively, means responsive to variations in pressure of the fluid in each conduit resulting from variations in the flow of fluid therethrough, said pressure responsive means being operatively connected to the valve coupling means whereby increase of flow in either conduit is adapted to partially close the valve in that conduit and to partially open the valve in the other conduit and means for varying the total combined flow from the mixing chamber.

5. In a carburetor for internal combustion engines, a conduit for fuel and a conduit for air, a mixing chamber in communication with the conduits and adapted to deliver into the intake of the engine, balanced variable opening valve means for each conduit adapted to control the flows therein, said valve means comprising a pair of coupled movable members and a pair of seat members adapted to be shifted with respect to the valve members and cooperating with the valve members, means for passing a flow in one direction through one of the valves and seats and in the opposite direction through the other of the valves and seats, coupling means for the valve means for each conduit whereby motion of one valve member toward closed or open position respectively imparts motion to the other valve member toward open or closed position. respectively, means responsive to variations in pressure of the fluid in each conduit resulting from variations in the flow of fluid therethrough, saidpressure responsive means being operatively connected to the valve coupling means whereby increase of flow in either conduit is adapted to partially close the valve means for that conduit and to partially open the valve means for the other conduit and means for shifting the seat members with respect to the valves to provide throttling.

6. In a carburetor for internal combustion engines, a mixing chamber, means for conducting a flow of fuel to the mixing chamber, means in said conducting means adapted to establish a differential pressure in the fuel flow, means for conducting a flow of air to the chamber, means in said conducting means adapted-to establish a differential pressure in the air flow, pressure-responsive means adapted to respond to the differential pressure in'the fuel line and pressure-responsive means adapted to respond to the differential pressure in the air line, variable opening valve means in the fuel line and valve means in the air line, the valves being coupled together such that opening of one tends to close the other, the valves being operatively connected with the said pressure-responsive means, whereby the valves are moved to different relative positions of opening by thepressure-responsive means until the forces exerted by the two pressure-responsive means are equal, whereupon a definite flow proportioning is established.

7. Apparatus for supplying two flows of fluids under pressure in constant relative proportion comprising conduit means for each fluid, means in each conduit means adapted to establish a differential pressure in each flow, pressure-responsive means responsive to differential pressures in each conduit andvariable opening valve means in each conduit coupled whereby opening of either valve tends to close the other, and so operatively connected to said valves that increase in the differential pressure in each conduit tends to close the valve in that conduit and to open the ,valve in the other conduit.

8. In a carburetor for internal combustion engines, a body member adapted for attachment to the intake of an engine and having an air passage extending therethrough to said intake, a liquid-fuel conduit terminating within said air passage for delivering fuel to the air flowing therethrough, a variable opening valve for controlling the fuel flow through said conduit, 'means for establishing a substantial differential pressure in the fuel conduit, means responsive to said differential pressure in the fuel, conduit connected to said valve and adapted to urge the valve in a direction to decrease the fuel flow through the conduit upon increase in said differential pressure, means for establishing a substantial fuel-air proportioning in substantially constant ratio is secured.

9. In a carburetor for internal combustion engines, an air passage, a manually operated throttle in the passage for varying the quantity of air supplied to the engine during periods of engine operation, a liquid fuel conduit terminating'in the passage for delivering fuel to the air flowing therethrough, a variable opening valve in the fuel conduit, means for establishing a substantial differential pressure in the fuel conduit anterior to said valve means responsive to said differential pressure in the fuel conduit and operatively connected with the valve and adapted to reduce the opening of the valve on increase of differential pressure in the fuel conduit, means for establishing a substantial differential pressure in the air passage anterior to the throttle, and means responsive to said difierential pressure in the air passage and operatively connected with the valve and adapted to increase the opening of the valve on increase of differential pressure in the air conduit.

10; In a carburetor for internal combustion engines a conduit for fuel and a conduit for air,

a mixing chamber in communication with the conduits and adapted to deliver into the intake of the engine, a variable opening valve in the fuel conduit, area restricting means for establishing a differential pressure in the fuel conduit, means responsive to said differential pressure in the fuel conduit and operatively connected with the valve and adapted to reduce the opening of the valve on increase of differential pressure in the fuel conduit, means for establishing a differential pressure in the air conduit, means responsive to said differential pressure and operatively connected with the fuel valve andadapted to increase the opening of the valve on increase of differential pressure in the air conduit, and means responsive to at least one of said difierential pressures for varying the effective area of the area restricting means.

11. In a carburetor for internal combustionengines, an air passage, a throttle controlling the passage and adapted to vary the quantity of air supplied to the engine during periods of operation, a liquid fuel conduit, a mixing chamber in communication with the air passage and fuel conduit and adapted to deliver into the intake of the engine, a variable opening valve in the conduit controlling the fuel flow therethrough, means for establishing a substantial differential-pressure in the air passage anterior to the throttle,

I combustion engine, an air passage, a fuel conduit, a mixing chamber in communication with the air-passage and fuel conduit and adapted to deliver intoltheyintake of the engine, a throttle controlling said passage, a variable opening valve in the fuel conduit, area restricting means for establishing a differential pressure in the fuel conduit, means for establishing a differential pressure'in the air passage anterior to the throttle, means. responsive to said differential pressure in the fuel conduit and means responsive to said differential pressure in the air passage operatively connected to said valve and arranged so: that an increase in the fuel differential will tend to decrease the fuel 'flow through the conduit and an increase in the air differential pressure will tend to increase the fuel flow through the conduit whereby the ratio of fuel and air supplied to the enginewill be maintained substantially constant, and means responsive to at least one of said diilerential pressures for varying the effective area of said area restricting means whereby the ratio of fuel and air supplied to the engine may be varied.

13. The invention defined in. claim 12 comprising in addition manually operable means for varying the effective area of said area restricting means to modify the ratio of fuel and air supplied to the engine.

. JOHN WEBB HOGG. 

